This is actually a very good question and is one that all homebrewers will encounter sooner or later.

As we have no data about your recipe I will not try to guess what you did or what may have happened.

Usually a Belgium Triple will call for an amount of candi sugar or other readily fermentable sugar and it is added to the boil to boost alcohol production and also to give the perception of a dry finish.

What temps are you mashing at?

What you will probably have to do is to try to add an amount of complex unfermentable sugars to your wort that will remain in the beer as residual sugars. One way to do this is to raise the temperature of your mash to around 154 -156 degF. This should result in a slightly sweeter beer with a some what bigger body in the end. You can also cut back on the candi sugars as well.

A bit of experimentation will be needed on your part so be sure to document your recipe changes and findings for each batch you brew. Also just change one item at a time then review the finished beer results.

Another way is to select a yeast that does not attenuate as much as the one that you are currently using. But please do strive for a fully fermented wort as you don't want to leave any fermentable sugars behind.

I think I would start by brewing another batch with the exact same recipe that you used before...and raise the mash temp up 3 or 4 degrees and see if the result is closer to what you are looking for.

Excellent advice right there. Keep good records, only change one thing at a time so you can pin point the changes, do too many things at once and you won't know which of the changes had the more desired result.

Ron,
I appreciate the follow up. Im mashing at ~158-160 currently. I have a recipie with a mixture of Belgian Pils, American 2 Row and just a pinch of Caramel malt. I currently use Candi as well as Honey in the fray. All of my Tripels a have finished at the targeted FG.

Im at the point where I have a beer that has the hop and spice structure of a Gouden Carolus, but im missing the very sweet aftertaste. Would adding dextrine malt increase the sweetness?

Thanks for posting the recipe. I think that I would cut the honey amount in half and change the yeast to a Wyeast 3522 Belgian Ardennes strain which attenuates slightly less than the yeast that you're currently using. And pitch it into the wort on the cool side...then let it slowly warm up to 69 to 72 degF towards the end.

If you try this, would you please keep us all informed as to your results?

It will be mid jan before I get to brew this again. My inventories are high. Just made a Pale Ale to be in the keg 1/1/08, and Im brewing a Corona clone for the morons down the street for new years. Im not going to put much love into this one.

I do appreciate the info. I was acutally checking out the Ardennes yeast the other day saying what if? If I cut the Honey, I will need to up the grain to keep the alcohol @ 9% right?

I added the 2 Row because its cheap. At the end of the day, Im finding that a good triple is mostly defined by hop and spice character. The grains cerytainly influence, but Imported grains are getting high.

I have heard that it is ok to use up to a total of 10% of your fermentables. I don't use all that much myself and usually try to add around 5% or less. Of course you will have to adjust the amount of base malt you use to still hit your target gravity correctly.